
package com.feib.soeasy.job.util;

import java.io.IOException;
import java.io.InputStream;
import java.io.PushbackInputStream;


/**
 * @title (#)UnicodeInputStream.java<br>
 * @description changed BOM recognition ordering (longer boms first)<br>
 * Original pseudocode   : Thomas Weidenfeller<br>
 * http://www.unicode.org/unicode/faq/utf_bom.html<br>
 * BOMs:<br>
 * 00 00 FE FF    = UTF-32, big-endian<br>
 * FF FE 00 00    = UTF-32, little-endian<br>
 * EF BB BF       = UTF-8,<br>
 * FE FF          = UTF-16, big-endian<br>
 * FF FE          = UTF-16, little-endian<br>
 * Win2k Notepad:<br>
 * Unicode format = UTF-16LE<br>
 * This inputstream will recognize unicode BOM marks
 * and will skip bytes if getEncoding() method is called
 * before any of the read(...) methods.<br>
 * Usage pattern:<br>
 * <code>
 * String enc = "ISO-8859-1"; // or NULL to use systemdefault<br>
 * FileInputStream fis = new FileInputStream(file);<br>
 * UnicodeInputStream uin = new UnicodeInputStream(fis, enc);<br>
 * enc = uin.getEncoding(); // check and skip possible BOM bytes<br>
 * InputStreamReader in;<br>
 * if (enc == null) in = new InputStreamReader(uin);<br>
 * else in = new InputStreamReader(uin, enc);<br>
 * </code>
 * @author Aki Nieminen<br>
 * @version 1.0.0 2010/11/25
 * @copyright Far Eastern International Bank Copyright (c) 2010<br>
 * @2010/11/24 create by Jimmy Liu<br>
 */
public class UnicodeInputStream extends InputStream {
    PushbackInputStream internalIn;
    boolean             isInited = false;
    String              defaultEnc;
    String              encoding;

    private static final int BOM_SIZE = 4;

    public UnicodeInputStream(InputStream in, String defaultEnc) {
        internalIn = new PushbackInputStream(in, BOM_SIZE);
        this.defaultEnc = defaultEnc;
    }

    public String getDefaultEncoding() {
        return defaultEnc;
    }

    public String getEncoding() {
        if (!isInited) {
            try {
                init();
            } catch (IOException ex) {
                IllegalStateException ise = new IllegalStateException("Init method failed.");
                ise.initCause(ise);
                throw ise;
            }
        }
        return encoding;
    }

    /**
     * Read-ahead four bytes and check for BOM marks. Extra bytes are
     * unread back to the stream, only BOM bytes are skipped.
     */
    protected void init() throws IOException {
        if (isInited) return;

        byte bom[] = new byte[BOM_SIZE];
        int n, unread;
        n = internalIn.read(bom, 0, bom.length);

        if ( (bom[0] == (byte)0x00) && (bom[1] == (byte)0x00) &&
                        (bom[2] == (byte)0xFE) && (bom[3] == (byte)0xFF) ) {
            encoding = "UTF-32BE";
            unread = n - 4;
        } else if ( (bom[0] == (byte)0xFF) && (bom[1] == (byte)0xFE) &&
                        (bom[2] == (byte)0x00) && (bom[3] == (byte)0x00) ) {
            encoding = "UTF-32LE";
            unread = n - 4;
        } else if (  (bom[0] == (byte)0xEF) && (bom[1] == (byte)0xBB) &&
                        (bom[2] == (byte)0xBF) ) {
            encoding = "UTF-8";
            unread = n - 3;
        } else if ( (bom[0] == (byte)0xFE) && (bom[1] == (byte)0xFF) ) {
            encoding = "UTF-16BE";
            unread = n - 2;
        } else if ( (bom[0] == (byte)0xFF) && (bom[1] == (byte)0xFE) ) {
            encoding = "UTF-16LE";
            unread = n - 2;
        } else {
            // Unicode BOM mark not found, unread all bytes
            encoding = defaultEnc;
            unread = n;
        }      
        

        if (unread > 0) internalIn.unread(bom, (n - unread), unread);

        isInited = true;
    }

    public void close() throws IOException {
        //init();
        isInited = true;
        internalIn.close();
    }

    public int read() throws IOException {
        //init();
        isInited = true;
        return internalIn.read();
    }


}
